Antibiotic and antibiotic resistance genes (ARGs) have been considered as emerging environmental contaminants and possess potential crisis to global public health. However, little is known about the differences between various configurations of two-stage combinations of constructed wetlands (CWs) on antibiotics and ARG removal from wastewater. In the study, three configurations of two-stage hybrid CWs (horizontal subsurface flow-down-flow vertical subsurface flow CWs, HF-DVF; horizontal subsurface flow-up-flow vertical subsurface flow CWs, HF-UVF; down-flow vertical subsurface flow-up-flow vertical subsurface flow CWs, DVF-UVF) were operated to evaluate their ability to remove high-concentration antibiotics (tilmicosin—TMS and doxycycline—DOC), ARGs (seven tet genes and three erm genes), intI1, 16S rRNA, and nutrients from goose wastewater. The results showed that all three hybrid CWs could remove more than 98% of TMS and DOC from wastewater, without significant difference among treatments (p > 0.05). For ARGs, DVF-UVF showed significantly higher removal efficiencies of intI1, ermB, ermC, ermF, tetW, and tetG compared to HF-UVF (p < 0.05), mainly because they might remove and arrest growth of bacteria. The relatively high removal efficiencies of NH4+-N, NO3—N, and NO2--N were also observed from DVF-UVF, ranging from 87% to 95% (p > 0.05), indicating that anaerobic ammonium oxidation (anammox) might be established in the CWs. Our results demonstrate that the removal performances of antibiotics using two-stage hybrid CWs are not affected by the combined configuration, whereas the combination of DVF and UVF CWs perform better on the removal of ARGs and nutrients compared with HF-DVF and HF-UVF CWs.

The goal of this study was to compare the effects of three plants (ryegrass, chicory and cress) in floating bed systems on purification of sedimentation pond wastewater (low-concentration) and biogas slurry (high-concentration) from geese farm in winter. The results showed that the floating bed with ryegrass had better removal rates on chemical oxygen demand (COD), total nitrogen (TN) and total phosphorus (TP) of low-concentration wastewater than other groups at 60 days (P<0.05), and the removal rates were 53.0%, 83.3% and 61.1% respectively. At 90 days, cress has the best performance on removing 5-day biochemical oxygen demand (BOD 5) and turbidity (P<0.05), with a removal rate of 82.9% and 80.8%. The removal rates of BOD 5 , COD, TN and turbidity by ryegrass in highconcentration wastewater were significantly higher than other treatments (P<0.05), which were 84.0%, 70.2%, 56.2% and 82.1% respectively. However, ryegrass had better stem height, root length and plant biomass production compared with cress and chicory. In conclusion, ryegrass was an optimal floating plant for purification of geese wastewater in winter and the optimal treatment time was 60 days. The regress has strong adaption for fluctuate concentrations of pollutants and is suitable for treatment of livestock and poultry wastewater in practice.

The goal of this study was to explore the optimal planting coverage rate and wastewater concentration required by water spinach floating bed system for the purification of geese farm wastewater. The results showed that the floating bed with water spinach in high concentration wastewater had better removal rates on ammonia nitrogen (NH 4 + -N), total nitrogen (TN) and total phosphorus (TP) (P<0.05). There was no significant difference on the removal of nutrients except turbidity (NTU) among the different plant coverage rages (P>0.05). The floating bed system with water spinach removed heavy metals (Hg, As and Zn) in different concentration wastewater, with removal rates of 22.21%~68.20%, 40.00%~52.94% and 100.00%. Water spinach in low concentration wastewater had significant higher root length, stem height and weight gain (P<0.05) than medium and high concentration wastewater. The TN and TP contents of water spinach stem leaf in high concentration wastewater were significantly higher than other groups(P<0.05). The concentration of heavy metals (Pb, Cd, As and Hg) in water spinach in all groups was far below the national food safety standard. In general, the water spinach floating bed is suitable for the purification of medium and low concentration wastewater, and the optimal coverage rate is 40%~60%.